Four sensor system for wheel alignment

ABSTRACT

A four sensor wheel aligner has a single omnidirectional angle sensor mounted on each of four vehicle support wheels. Each sensor is in optical communication with the other sensors. Data is produced from which toe, camber, caster and steering axis inclination angles are computed. No reference is made to vertical. Redundant data sets are produced which provide system reliability and error tracking features and maximum accuracy from available data sets. Frame distortion measurements are made to facilitate collision repair in coordination with wheel alignment.

This application is a CIP of application Ser. No. 08/674,366 filed Jul.2, 1996, U.S. Pat. No. 6,181,993, which is a continuation of applicationSer. No. 07/961,945, filed Oct. 16, 1992, abandoned.

SUMMARY OF THE INVENTION

This invention relates to a wheel alignment system for vehicle wheelswherein a single means for angle measurement means is mounted inpredetermined relationship to the plane of each of four vehicle supportwheels. The angle measurement means provides wheel angle indicativeoutput signals in redundant signal sets and wherein any signal setcontains data sufficient to obtain alignment angles. Further means areprovided for receiving and processing the redundant signal sets and forindicating alignment angles for the support wheels.

A wheel alignment system is disclosed herein for a vehicle having atleast four support wheels wherein single omnidirectional anglemeasurement means is mounted on each wheel in known orientation with theplane of the wheel for determining the spatial angles relating to toeand camber between the planes of the wheel on which mounted and aprojected energy beam and providing projected beam angle indicativesignals corresponding thereto. Means is provided for receiving andprocessing the angle indicative signals for providing signals indicativeof toe and camber alignment angles between the planes of the supportwheels.

A wheel alignment system is disclosed herein for a vehicle having atleast four support wheels wherein angle measurement means is mounted oneach wheel in predetermined relationship with the plane of the wheel forproviding wheel angle indicative output signals in redundant signalsets. Any signal set contains data sufficient to obtain desired wheelalignment angles. Further means is included for prioritizing the signalsets in the order of potential wheel alignment angle accuracy. Means isalso included for selecting the highest accuracy priority signal setavailable and for processing the highest accuracy signal set availableto obtain the desired wheel alignment angles.

An omnidirectional angle measurement apparatus is disclosed herein whichincludes spheroid-like mounting means having a plurality of mountingpositions on the surface thereof, wherein each position is oriented inpredetermined spatial position relative to a polar axis of the mountingmeans. A plurality of beam emitting means is provided for individualmounting at ones of the plurality of mounting positions for emittingenergy beams in predetermined spatial directions relative to the polaraxis. Means is included for receiving the energy beams and foridentifying the spatial direction of received beams toward said meansfor receiving relative to said polar axis.

An omnidirectional angle measurement apparatus is disclosed whichincludes mounting means having a polar axis and a plurality of mountingpositions thereon. A plurality of beam emitting means are secured atones of the plurality of mounting positions so that the beam emittingmeans project beams omnidirectionally in predetermined directionsrelative to the polar axis. Means is included for sequentially excitingthe beam emitting means and for providing an emission sequence signalcorresponding thereto. Means is also provided for receiving theprojected beams and the emission sequence signal to thereby identify theprojection directions of the received beams relative to the polar axis.

An omnidirectional measurement apparatus is disclosed herein whichincludes at least two beam receiver means mounted in spaced positionsand a mounting base positioned in a known location having at least twolight sources mounted in known position in the mounting base andemitting beams extending in directions separated by a known angle. Meansis also provided for sweeping the emitted beams from the two lightsources cyclically through an angle large enough to impinge upon each ofsaid beam receiver means.

Further, an angle measurement apparatus is disclosed for measuringangular relationship between a plurality of adjustably interconnectedmembers without reference to vertical. Omnidirectional beam projectormeans is mounted in known orientation relative to each member. Beamreceiver means is mounted on each member for receiving projected beamsand for providing beam reception signals. Means is provided forreceiving and processing the beam reception signals and for providingmember relative angular orientation in at least two substantiallyorthogonal planes.

A vehicle wheel alignment system for use on level or non-level vehiclesupport surfaces is disclosed which operates to align wheels on avehicle having at least four support wheels with defined wheel planes.Omnidirectional beam projection means is mounted on each support wheelin known orientation with the wheel plane. Beam reception means ismounted in known position on each support wheel providing beam receivedsignals when impinged by a projected beam. Also included is means forreceiving the beam received signals and for determining the spatialangles between a wheel plane and a beam projected from theomnidirectional beam projection means mounted on one support wheeltoward the beam reception means mounted on another support wheel.Further, means is included for combining the determined spatial anglesfor obtaining wheel alignment angles in the wheel reference planes forthe four support wheels.

A wheel alignment system has been developed for a vehicle having leftand right front and left and right rear wheels having wheel planessubject to alignment adjustments. The system includes first means formeasuring the line of sight angles between the plane of the left frontwheel and the planes of the right front, left rear, and right rearwheels. Further, second means is included for measuring the line ofsight angles between the plane of the right front wheel and the planesof the left front, right rear, and left rear wheels. Processor means isprovided for receiving the line of sight angle measurements from thefirst and second means for measuring and for providing output indicativeof the relative orientations of the left and right front and the leftand right rear wheel planes.

A wheel alignment system is disclosed for a vehicle having four wheelswith wheel planes subject to alignment adjustment which includes firstwheel mounted means for measuring the line of sight angles between theplane of a first wheel and the planes of second, third and fourthwheels. Processor means is provided for receiving the line of sightangle measurements from the first wheel mounted means for measuring andfor providing output indicative of the relative orientations of the fourwheel planes.

A wheel alignment system is disclosed herein for measuring wheelalignment angles of front and rear wheels, wherein the system includesfirst and second means for measuring angles mounted on and inpredetermined orientation with the left and right front wheels, andthird and fourth means for measuring angles mounted on and inpredetermined orientation with the left and right rear wheels. Thefirst, second, third and fourth means for measuring angles are inoptical communication with each other, whereby line of sight anglemeasurement outputs are produced by each means for measuring angles.Processor means is provided for receiving the line of sight anglemeasurement outputs and for providing output indicative of the relativeorientations of the front and the rear wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic plan view of a four wheel vehicle showing aninstallation of one embodiment of the present invention.

FIG. 2 is an elevation of the diagrammatic view of FIG. 1.

FIG. 3 is another diagrammatic plan view of additional aspects of theinvention.

FIG. 4 is a section view of one embodiment of the omnidirectional anglemeasurement device.

FIG. 5 is a three-view depiction of a solid state embodiment of theomnidirectional angle measurement device of the present invention.

FIG. 6 is a perspective diagram of one type of directional energy beamreceiver which may be used in the present invention.

FIG. 7 is a block diagram of the embodiment shown in FIG. 1.

FIG. 8 is another block diagram of an embodiment of the inventionincluded in FIG. 1.

FIG. 9 is yet another block diagram of an embodiment of the inventionincluded in FIG. 1.

FIG. 10 is a diagram of one face of the omnidirectional anglemeasurement device of FIG. 5.

FIG. 11 is a graph of luminous intensity as a function of energy beamcone angle for one beam sensor useful in the present invention.

FIG. 12 is an intensity ratio diagram relating to a sub space of theface of FIG. 10.

FIG. 13 is another intensity ratio diagram for a sub space of the faceof FIG. 10.

FIG. 14 is another intensity ratio diagram for the same sub space of theface of FIG. 10.

FIG. 15 represents a solution within the sub space of the face of FIG.10.

FIG. 16 represents a solid angle projection map for one of theprojectors of FIGS. 4 or 5 showing latitude or tilt angle on theordinate and longitude or rotation angle on the abscissa.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 of the drawings, a vehicle frame 20 is shown whichis supported by four support wheels represented by the wheel planes A,B, C and D. An angle measuring device, to be hereinafter described, ismounted in known orientation to each one of the support wheel rotationplanes. These angle measurement devices are represented in FIG. 1 by theitem nos. 21, 22, 23 and 24 in known orientation to wheel planes A, B, Cand D respectively. A scaling factor function is provided for theembodiment of FIG. 1 by placement of a receiving device 26, such as aretro reflector, at a known distance d away from angle measurementdevice 22 on wheel plane B. The distance d is known and the angle θ ofFIG. 1 may be measured by the angle measuring device 21. Consequentlythe distance from angle measuring device 21 to angle measuring device 22may be computed. Since angles 1 through 12 of FIG. 1 are measurable bythe angle measuring devices 21 through 24, all other distances betweenmeasuring devices are known through the construction of similartriangles. It should be noted that the angles 1 through 12 are measuredline of sight, whether they require lines of sight across, along ordiagonally of the vehicle frame 20.

As may be seen in FIG. 1, angle 1 represents the angle in plan view(toe) between wheel plane A and the direction from angle measurementdevice 21 directly to angle measurement device 23. When a beam isprojected by angle measurement device 21 and received by anglemeasurement device 23 the angle 1 is described with respect to wheelplane A. In like fashion when a beam is projected from the anglemeasurement device 23 to be received directly by angle measurementdevice 21 angle 3 of FIG. 1 is described with respect to the plane C ofthe left rear support wheel of the vehicle. The remaining angles 4through 12 as shown in FIG. 1 are obtained in similar fashion includingthose angles between the wheel planes in the diagonal directions betweenthe left front and right rear of the vehicle represented by angles 11and 12 and between the right front and left rear represented by angles 9and 10. The angles measured in the view of FIG. 1 may be consideredangles in yaw and when combined will provide wheel toe.

FIG. 2 is an elevation view of the embodiment of FIG. 1 taken at theforward end of the frame 20. The angle measurement devices 21 and 22 inFIG. 2 are capable of measuring angles in roll or camber as representedby angles 13 and 14 of FIG. 2. The planes A and B of the front wheelssupporting the frame 20 have spin axes 27 and 28 respectively depictedin FIG. 2. A beam projected directly between angle measurement means 21and 22 forms one side of the angles 13 and 14 and as depicted in FIG. 2extends to the spin axes 27 and 28 of each of the wheels A and B,respectively. Thus, it may be seen that the angle measurement means 21and 22 provide angular data from which camber angles of the supportwheels will be obtained. It should be noted that the alignment anglesreferred to herein are with reference to the wheel reference planesrelative to the support wheel set and have no relation to localvertical. As a result, the system performs alignment on non-levelsupport surfaces for the vehicle as well as level support surfaceswithout need for a local vertical sensor. Additionally the anglemeasurement devices disclosed herein are capable of measuring angles inpitch as may be perceived by visualizing a side elevation similar to thefront elevation of FIG. 2.

It may also be seen in FIG. 2 that ride height may be obtained throughuse of the disclosed system. Since the positions of the anglemeasurement devices 21 and 22 are known relative to a ride heightreference point 33 on the vehicle chassis, angle measurements may bemade between measurement devices 21 and 22 and receiving devices 29 and31 mounted on an underlying support plane 32. Solution for ride heighth₁ is made from knowledge of the distance between the receivers 29 and31 and the measured angles.

When the ride height for a vehicle is specified between a point on thesuspension and a point on the body represented by the points 36 and 37respectively in FIG. 2, similar angle measurements made betweenreceiving devices placed at the points 37 and 36 and the angle measuringdevices 21 and 22 provide angular data sufficient to compute thespecified ride height between the suspension and the body represented byh₂.

In view of the description given hereinbefore, the angle measurementdevices of FIGS. 1 and 2 may be used to determine steering axisinclination and caster angles. To accomplish this for steering axisinclination steerable wheels are turned to an arbitrary turn angle andthe measurement of the turn angle is made. The wheels are then turned toanother arbitrary turn angle, the angle measured and the difference inpitch (as projected on a longitudinal plane) at the two yaw angles, iscomputed. The well known relationship using the pitch difference is usedto obtain steering axis inclination. Caster angles may be obtained byobtaining the change in roll angle (as projected on a lateral plane) atthe two known yaw or turn angles and then using the well knownrelationship between the measured angles and caster.

Turning to FIG. 3 of the drawings, points 38 and 39 are known to be onthe centerline of the chassis 20. The angle as measured from each of theangle measurement devices 21 and 22 to each of the points 38 and 39 willprovide sufficient data to construct the centerline of the vehiclerelative to the position of the wheel rims A, B, C and D. A center lineof the vehicle may also be determined if access to the centerline of thechassis 20 is not available if angles are measured between twomeasurement devices and a pair of points equidistant from the centerlineof the vehicle chassis 20. In such a case measurements may be made ofthe angles between angle measurement devices 23 and 24 and points 41 and42 known to be equidistant from the chassis centerline as well asbetween devices 23 and 24 and points 43 and 44 also equidistant from thecenter line. As a result data is provided from which the chassiscenterline may be obtained. The points 38, 39, 41, 42, 43 and 44 mayhave retro reflectors or optical receivers of various kinds, forexample, mounted thereat for accomplishing angle measurements.

In FIG. 3 the angle θ may be measured by measurement device 21. Theangle has as one side the line between devices 21 and 22. The otherangle side is the distance between device 21 and receiver 26. Thedistance d is known. The distance from device 21 to device 22 may thenbe computed. All other distances between wheels may then be calculatedusing similar triangles.

As further seen in FIG. 3, two points P₁ and P₂ on a vehicle frame Cchannel 46 are shown in optical communication with at least two of theangle measurement devices 21, 22, 23, 24. As shown, devices 22 and 24measure angles from which space coordinates X₁Y₁Z₁ and X₂Y₂Z₂respectively are calculated from the measured angles, because the anglesensors, to be hereinafter described, are capable of measuring angles inspace which may have pitch, yaw and roll components relative to thevehicle support wheels ABCD. A plurality of points such as P₁ and P₂ maybe located to see if the C channel is straight or the location of thepoints may indicate a shift from the normal position of the channel. Asa result, frame collision damage may be assessed and repairs made priorto undertaking wheel alignment.

With reference now to FIG. 4 of the drawings an electro mechanicalomnidirectional angle measurement device is shown. A framework 48 isshown in which is mounted a rotation driver 49 having a shaft 51extending from one end. An angle encoder 54 has a shaft 53 extendingtherefrom which is coupled to shaft 51 by a coupler 52. The encoder 54is also mounted in the frame 48. The rotation driver has another shaft56 extending from the side opposite shaft 51 which has a reflector 57mounted for rotation thereon to provide the above-discussed means forsweeping emitted beams cyclically through an angle large enough toimpinge upon beam receiver means. A reflecting face 58 on the reflectorcauses energy beams from light emitting diodes or laser transmitters 59,61 and 62 to be transmitted from face 58 as shown. The beams from thesetransmitters are emitted in known sequence so that a received beam maybe identified. The beam transmitters are mounted in the frame 48 asshown and a revolving beacon of diverging beams results when thereflector is rotated. The emitting devices 59, 61 and 62 are mounted asshown in the overhanging portion of the frame 48 so that they projectbeams at approximately 0 degree reference direction as well as above andbelow the 0 degree reference direction by some known angle in the rangeof ±30 degrees. It may be said that the beams emit from the surface of asphere at substantially 0 degrees of latitude and 20 to 30 degrees oflatitude above and below 0 degrees. The beams will be projected throughthe surface of the sphere repeatedly through 360° of longitude as thereflector 57 is rotated. It may be seen that the measurement device ofFIG. 4 is omnidirectional inasmuch as the projector transmitsmultiplexed beams in multiple directions in space together with anencoder signal indicating instantaneous projection direction and beamidentification so that the projection angle of a received beam isdetermined. Directional interpolation of the beams, as hereinafterdescribed, to determine a direction from a projector to a receiverprovides a true omnidirectional feature.

FIG. 5 shows another embodiment of an omnidirectional measurement devicewherein a plurality of LED's or laser beam projectors are arranged onthe surface of a spheroid-like solid 63 to project energy beams in knowndirections relative to the orientation of the solid. The spheroid-likesolid shown in the preferred embodiment of FIG. 5 is illustrated by acentral top view and two elevation projections of the device. The solidas shown in FIG. 5 has a number of faces. It will be described as aspheroid-like solid having a polar axis A-B. A centrally located plane,seen on edge as line 64, represents an equator of the spheroid-likeshape as it intersects the surface thereof. The solid illustrated inFIG. 5 has twenty faces which are equilateral triangles. The beams areprojected radially from the spheroid through the points or intersectionsof the equilateral faces. The LED generated beams are conical in shapeand are either known or determinable.

The projectors are arranged on the surface of the spheroid-like solid sothat the center of the cone of each beam is projected along a radialline from the center of the spheroid-like solid through the points onthe surface C,D,E,F,G,H,I,J,K,L. As a result beams are projected fromthe angle measurement device 63 of FIG. 5 at angles approximately 27°north latitude relative to an equator 64 and at approximately 27° southlatitude relative thereto. Five energy beam projectors are located atthe north latitude and five are located at south latitude. The north andsouth latitude located projectors are staggered so that a beam isprojected every 36° of longitude around the spheroid-like shape of FIG.5. The poles of the solid of FIG. 5 are at the points designated A and Bas mentioned hereinbefore and serve as a reference for mounting theangle measurement device in known location rotationally and with regardto its polar axis relative to a supporting wheel plane represented bythe planes A, B, C and D of FIG. 1. While no projectors are mentioned inFIG. 5 at points A or B (the poles), such projectors could be includedif the situation warranted. Moreover, a greater number of projectors anddifferent face configurations for the spheroid could be provided. In anyevent, the projectors are energized sequentially and a signal isprovided by the energizing source which indicates which projector isemitting a beam at any instant.

It may be seen that the beam projector of FIG. 5 is also anomnidirectional beam projector in view of the multiple beam projectionsin known directions in space. Directional interpolation from beamidentification is disclosed herein in conjunction with FIGS. 10 through16. The beams are energized in a known sequence as mentioned before sothat the rotating beam solid angle projection direction is known at anypoint in time. When beams are received at spatial points of interest, aprojection direction for the received beam is thereby determined.Accuracy of 0.05 degrees in selected ranges and 0.10 degrees in theremainder of the range appears feasible. An LED beam projector for usein the omnidirectional angle measurement device of FIG. 5 is HewlettPackard HLMP-7019.

With reference now to FIG. 6 of the drawings a three axis coordinatesystem is shown having an angle sensitive receiver 66 aligned with the Zaxis and an angle sensitive receiver 67 aligned with the X axis. Acylindrical lens 68 is placed in the path of an impinging projected beam69 ahead of the angle sensitive receiver 66. Another cylindrical lens 71is placed in the path of beam 69 in front of the angle sensitivereceiver 67. As a result a line of light 72 is created which fallsacross the angle sensitive receiver 66 and another line of light 73falls across the angle sensitive sensor 67. Consequently, the center ofthe cone of light projected by one of the beam projectors C through L(FIG. 5) is known to impinge the receiver at the point X,Z. The beamreceiver of FIG. 6 is described herein to illustrate one type ofdirectional beam receiver to determine the direction from which theenergy beam has arrived at the point of reception. As will behereinafter described, an angle measurement device as defined hereinincludes a beam projector and type of directional receiver such asillustrated in FIG. 6 or a combination of one of the omnidirectionalbeam projectors of FIG. 4 or 5 together with a non directional beamreceiver or a combination of an omnidirectional beam projector and adirectional receiver. Such angle measurement devices are referred toherein as single devices for measuring angles to distinguish oversystems which employ more than one angle measurement device on a vehiclewheel such as multiple optical projectors and receivers and gravitysensing devices. A typical sensor represented by the directional sensors66 and 67 is the L30 sensor manufactured by SiTek Electro Optics,Sweden, marketed in the U.S.A. by EG and G Foton Devices, Salem Mass.

Turning now to FIG. 7 of the drawings a measuring device is shown foreach of the support wheels designated by the blocks TXA, TXB, TXC andTXD. As described hereinbefore, the time at which the omnidirectionalbeam projector projects a beam is known and a specific spatialprojection direction relative to a support wheel plane of rotation isassigned to each beam. Beams are projected from beam projector TXA, forexample, to be received by the non directional receiver mounted on oneor the other three support wheels represented by the blocks RXB, RXC,RXD in the diagram of FIG. 7. When non directional receiver RXB receivesa projection beam from TXA for example, the intensity of the beam isdetected at a high luminous intensity beam detector 75 shown in theblock connected to non directional receiver RXB. Several beams arereceived, the higher intensity beams being closer to being in a directline of sight from the omnidirectional projector to the non directionalreceiver. The three highest intensity beams in this embodiment areprocessed in a fashion to be hereinafter described to produce angle 5 asseen in FIG. 1. In like fashion the beam projector at each wheelprojects beams toward the non directional receivers on each of the threeother support wheels and the higher intensity beams are recognized to beprocessed and to produce data from which each of the other anglesdepicted in yaw in FIG. 1 and in roll in FIG. 2 may be computed. Themeasured angles for the projected beams extending between the beamprojectors and the non directional beam receivers are processed in acomputer 74 in FIG. 7 to provide relative angular orientation betweenthe planes of the wheels A, B, C and D and the direct projectiondirection to the non directional receiver. These angles are thenprocessed and the results are displayed in terms of desired alignmentangles by a display 76.

It may be seen from FIGS. 7 and 1 that redundant sets of anglemeasurements may be obtained from which the desired alignmentcharacteristics may be determined. For example, angles as describedherein from the left rear wheel of the vehicle around the front to theright rear wheel of the vehicle are sufficient for obtaining toe anglesof the four support wheels. In like fashion, measurement of angles fromthe left front wheel around the rear of the vehicle to the right frontwheel are also sufficient to obtain toe alignment angles for all foursupport wheels. Numbers of other combinations for determining toe of allfour support wheels as well as camber and other alignmentcharacteristics are present if all measurements are made in theembodiment of FIG. 1 as shown in the block diagram of FIG. 7. Total reartoe, however, is most accurately measured when measured directly as inthe case when angles are measured from the front wheel of the vehiclearound the rear wheels of the vehicle to the opposite front wheel. Sucha data set would be preferred for rear toe measurement because it ispotentially more accurate and therefore would be assigned a higherpriority by the system. Complete data sets which are redundant areprioritized by the computer in accordance with potentially higheraccuracy measurement. Alternatively, data sets may be prioritized inaccordance with some other criteria which may be controlled by anoperator of the system or contained within the controlling program. As aresult, each data set is recognized and prioritized by the system andthe highest priority data set, depending on the prioritization, isselected to be processed to provide the alignment characteristics in thedisplay 76. In the examples given, angle measurements at wheels aroundthe front of the car and angle measurements at wheels around the rear ofthe vehicle, the optical path between the rear wheels, which wouldordinarily be given highest priority for rear wheel toe, measurementsmight be blocked. Since that data set would be incomplete, the nexthighest priority complete data set would be automatically selected to beprocessed and to provide the basis for the display of alignment angles.Additionally, when all or several complete data sets are available theymay be used in separate computations of the alignment angles andcompared for acceptable error tolerances between the alignment systemcomponents

The block diagram of FIG. 8 shows the configuration wherein one anglemeasurement device TXA is such as shown in FIGS. 4 or 5 and the otherthree angle measurement devices RXB′, RXC′, and RXD′ are directionalbeam receivers such as shown in FIG. 6. The receivers provide outputwhich is used to determine the angles of projection from TXA (angles 5,1 and 11) through the high intensity detectors as described inconjunction with FIG. 7. The receivers also provide output which is adirect indicator of the angles of impingement (angles 6, 3 and 12 ofFIG. 8) of the projected beams relative to the wheel plane on which thedirectional receiver is mounted. The embodiment of FIG. 8 providesenough data for toe camber, SAI and caster alignment angle determinationas described hereinbefore, but does not provide redundant data.

The block diagram of FIG. 9 shows an embodiment where the anglemeasurement devices 21 and 22 of FIG. 1 are omnidirectional anglemeasurement projectors and the angle measurement devices 23 and 24 aredirectional beam receivers. The angles indicated in FIG. 9 aredetermined in the same fashion as described for FIG. 8 except that alarger number of angles are provided thereby affording some redundancyin data. As indicated in FIG. 9, the directional receivers RXC′ and RXD′receive the projected beams from omnidirectional transmitter TXA and theangles 1 and 11 are obtained through the use of the high intensitydetectors 75 while the angles of impingement 3 and 12 are measureddirectly using the signals from RXC′ and RXD′. In the same fashion,angles 10 and 2 of FIG. 1 are obtained by the cooperation of TXB, RXC′,RXD′ and high intensity detectors 75, while angles 9 and 4 are obtainedby processing directly the output signal from RXC′ and RXD′. As with theembodiments of FIGS. 7 and 8, the processed angle signals are utilizedin algorithms by computer 74 to provide the alignment data of interestcalled upon by the system on display 76.

It may be seen from the foregoing that the concept disclosed hereinincludes the embodiment having omnidirectional angle sensing devices onthree vehicle wheels and a directional receiver on the fourth vehiclewheel.

FIG. 10 shows one face of the spheroid-like solid depicted in the threeviews of FIG. 5 wherein the face is seen at the left of the lower view.The equilateral triangle EIJ which bounds the face is shown in FIG. 10for the purpose of illustrating how the received projected beams areidentified and how interpolation is performed to locate the direction inspace relative to a wheel plane of the omnidirectional energy beingreceived. The receiver output signal is passed to the high intensitydetector 75 which identifies, as mentioned hereinbefore, the highestintensity beams in a number of serially received beams and ranks thereceived beams in order of luminous intensity. The equilateral triangleshown in FIG. 10 is divided into three subspaces 81, 82 and 83 bydrawing the bisector of each side of the triangle EIJ. As mentionedearlier, the projection direction of the beams from the beam projectorof FIG. 5 through each apex of triangle EIJ is known relative to thepolar axis of the spheroid-like solid of FIG. 5. The purpose of thesubspaces is to provide an area within which may be located, byinterpolation, a point on the surface of the spheroid through which aprojected radial beam would pass to impinge directly on the receiver.

Each beam has a conical beam shape wherein the luminous intensity of thebeam diminishes when the beam is detected at an angle of departure fromthe polar axis of the cone. FIG. 11 shows this diminishing luminousintensity as a function of departure angle. This characteristic is usedin the following described interpolation process for finding theprojected radial beam of interest.

In the example used here, the highest intensity beam received isprojected from apex E, the next highest from apex J and the thirdhighest from the apex I. Three ratios of highest beam intensities areused here, although two, four or more could be used if desired. FIG. 12shows the loci of points of constant intensity ratios of beam E to beamJ. They are thought to be parabolic. Several curves of constantintensity ratio are shown passing through subspace 81 because that isthe area of interest since beam E is of highest intensity. For sake ofthis example, a ratio of E to J of 1.7 is calculated. FIG. 13 shows aratio of E to I intensity of 1.5 in subspace 81. A ratio of J to I(second to third intensity) of 1.7 is sensed, which also passes throughsubspace 81 as seen in FIG. 14. All three loci intersect substantiallyat point 84 as seen in FIG. 15. Thus, the projected radial beam whichwould pass through the spheroid-like solid 63 of FIG. 5 at the point 84in the face bound by EIJ represents the beam direction in space which issensed by the non-directional sensor at an opposing wheel or by adirectional sensor at an opposing wheel when it performs the function ofsensing the projection direction of the beam received.

FIG. 16 shows a solid angle graph which may be used as a substitute forthe method of determining the direction of the radial beam of interestdescribed in conjunction with FIGS. 12-15. As seen in FIG. 16, a plot oftilt angle or latitude angle appears on the ordinate and a plot of therotation angle or longitude angle appears on the abscissa. The abscissashows that the omnidirectional beam projector travels through 360°. Theordinate shows that the directional projected beams are at approximately27° north latitude (plus 27°) and 27° south latitude (minus 27°). A zerotilt angle line represents the equator 64 of the spheroid like solid ofFIG. 5. Relative intensities are plotted on the graph of FIG. 16 whereinthe beam projected along the direction through the point E in FIG. 5 ismost intense, through the point J is second in intensity and throughpoint I is third in intensity. Interpolation on the graph of FIG. 16provides the same point 84 for the projection direction directly fromthe omnidirectional beam projection device to the receiver which hassensed the aforementioned relative luminous intensities.

Several algorithms are necessary for a description of the specific beamprojector utilized which will describe the relationship of the luminousintensity as a function of angular deviation from the polar axis of theprojected conical beam. Additionally, loci of points representingconstant ratios of luminous intensity must be defined for the specificbeam projectors used. An algorithm for converting measured intensityratios into subspace location is necessary. Once a certain number ofsignals representing highest luminous intensity projected beams areselected, the intensity levels must be ranked from the highest to thelowest of interest. Ratios must then be calculated between the highestand second highest, highest and third highest, and second highest andthird highest. The aforementioned constant ratio algorithms may then beused to determine the position in subspace through which a radial beammust pass thereby obtaining the spatial direction of the beam. Thealgorithms for converting angular measurements between projected beamsand wheel planes into alignment angles using similar triangles are thendefined. All measurements are undertaken using the planes of the supportwheels as reference instead of a gravity vector. Chassis diagonal lineof sight measurements determine vehicle geometric shape and provideredundant measurements for monitoring the accuracy of the other anglemeasurements. The angle measurement means 21-24 are all mounted at themid wheel height. All angles and alignment data are referenced to thewheel planes of the support wheels and are referenced to the vehicleframe by means of retroreflectors or receivers mounted at known pointson the frame. The absolute position of the wheels relative to the frameis obtained through the use of a scaling device. Specific beam projectorluminous intensity characteristics may be measured and stored for use ininterpolating between beam projectors for defining specific directionsfrom a beam projector to a beam receiver.

The system described herein provides alignment angle data redundancy fortoe. Measurements in yaw, roll and pitch are made at each wheel and aprioritization scheme of the redundant data sets is predetermined in thesystem instructions. Alignment may be performed on non level racks or onnon level ground because there is no vertical reference necessary forthe system. Frame reference measurements may be made between the supportwheels and the vehicle chassis prior to alignment adjustment of thesupport wheels so that collision repairs may be undertaken if it appearsa portion of the deviation from alignment specification is due tochassis/frame damage. Redundancy may be obtained for vehicle chassisdata if more than two angular measurement instruments are incommunication with points on a frame member, such as points P1 and P2.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:
 1. An omnidirectional angle measurement apparatuscomprising: spheroidal mounting means having a plurality of mountingpositions on the surface thereof, wherein each said position is orientedin predetermined spatial position relative to a polar axis of saidmounting means, a plurality of beam emitting means omnidirectionallmounted at ones of said plurality of mounting positions for emittingenergy beams in predetermined spatial directions relative to said polaraxis, means for receiving said energy beams and for identifying thespatial direction thereof toward said means for receiving relative tosaid polar axis.
 2. An omnidirectional angle measurement apparatus as inclaims 1 wherein said means for receiving comprises: non-directionalbeam sensitive means providing receiver output responsive to beamreception, and means for identifying received beams and forinterpolating spatial angles from said emitters directly to said meansfor receiving.
 3. An omnidirectional angle measurement apparatuscomprising: mounting means having a polar axis and a plurality ofmounting positions thereon, a plurality of beam emitting means securedat ones of said plurality of mounting positions so that each of saidbeam emitting means projects a plurality of beams omnidirectionally inmultiple predetermined directions relative to said polar axis, means forsequentially exciting said beam emitting means and for providing anemission sequence signal, and means for receiving said projected beamsand said emission sequence signal for identifying the projectiondirections of received beams relative to said polar axis.
 4. Anomnidirectional angle measurement apparatus comprising: at least twobeam receiver means mounted in spaced positions, a mounting basepositioned in a known location, at least three light sources mounted inknown positions in said mounting base and emitting beams extending indirections separated by a known angle, and means for sweeping saidemitted beams from said at least three light sources cyclically throughan angle large enough to impinge upon each of said beam receiver means.5. An omnidirectional angle measurement apparatus as in claim 4, whereinsaid at least two beam receiver means comprises a plurality of beamreceivers mounted individually on different members, whereby individualangles between said mounting base and said different members aremeasured.
 6. An angle measurement apparatus for measuring angularrelationship between a plurality of adjustably interconnected memberswithout reference to vertical, comprising: omnidirectional beamprojector means mounted in known orientation relative to each saidmember for projecting a plurality of beams in multiple directions inspace, beam receiver means mounted on each said member for receivingsaid projected beams and for providing beam reception signals, and meansfor receiving and processing said beam reception signals and forproviding member relative angular orientation in at least twosubstantially orthogonal planes.